<obout:OboutTextBox runat="server" ID="txt1" OnTextChanged="txt1_TextChanged" ... />
protected void txt1_TextChanged(object sender, EventArgs e) { label1.Text = "The text was modified to: " + txt1.Text; }
Protected Sub txt1_TextChanged(ByVal sender As Object, ByVal e As EventArgs) label1.Text = "The text was modified to: " + txt1.Text End Sub